The present invention relates to a countertorque rotor for helicopters. In particular, the present invention relates to a countertorque rotor having a simple and rapid balancing system.
In countertorque rotors for helicopters it is known to utilise a tubular hub carrying at its axial ends two blades and provided centrally with two oblique coaxial tubular projections within which there is axially slidably mounted a transverse shaft centrally keyed onto one end of a drive shaft which extends into the interior of the hub through a radial hole formed therein.
In the known rotors described above the said transverse shaft is maintained in a fixed axial position within the said two tubular projections by means of two closure covers fitted to the free ends of the tubular projections and traversed by respective central axial screws which engage associated threaded axial holes formed on the opposite ends of the said transverse shaft.
On each of the said screws there is normally mounted a plurality of thin washers in a stack between the associated end of the said transverse shaft and the relative cover. The presence of these washers permits the dynamic balancing of the rotor about the axis of the drive shaft, which can be effected by taking off the said covers and moving one or more washers from one side to the other of the said transverse shaft. In fact the displacement of a washer corresponds to an equal displacement in the opposite sense of the hub with respect to the drive shaft in the direction of the axis of the said transverse shaft.
From what has been described above it is clearly apparent how the balancing procedure of the known countertorque rotors described above normally requires the repeated removal and replacement of the said two covers and is, because of this, particularly time consuming and complicated.